Bracuiopopa. | UPPER PALAZOZOIC MOLLUSCA. 455 
the shell very thick ; internal surface marked with close, quincuncially arranged, very large, spinulose tubercles. 
Width seven lines, proportional length =, depth (greatest a little in front of middle) = to =. 
M. de Koninck is of opinion that this species should be referred to the Leptena variolata of @Orbigny, but 
the characters which M. d’Orbigny gives to separate that species from Leptena sarcinulata separate it equally 
from this; and I feel unwilling to make the rapprochement. At the same time it is peculiarly unfortunate that 
Mr Phillips should have mixed up the Devonian and carboniferous species in his figures and descriptions of this 
species ; however, I think with MM. de Koninck, Murchison, Verneuil and Keyserling, and other continental 
writers, that his Devonian specimens were the C. sarcinulata (Schlot.); the name Hardrensis, and the figures 
I have quoted, are clearly stated to be of the carboniferous form, which may well bear this name. 
Position and Locality.—In the carboniferous limestone of Craige, near Kilmarnock. 
LepT@NA (Chonetes) PAPILIONACEA (Phill. Sp.) 
kef. and Syn.= Spirifera papilionacea Phill. Geol. York. t. 11. f. 6 = Ohonetes papilionacea de Koninck. Monog. 
Chonetes, t. 19. f. 1. + C. comata id. id. f. 2. (not Productus comoides Sow.) 
Desc.—Semicircular, flattened when young ; hinge-line equal to the width of the shell, forming acute semi- 
elliptical ears; the hinge-line and sides meeting at an angle of 70°; the beak is very small, and scarcely pro- 
jecting beyond the hinge-line; conyexity of the middle of the shell varies considerably, but is generally small, 
and passes gradually into the flattened sides; at about an inch from the beak, or as the shell begins to acquire 
its adult form, a few irregular rounded longitudinal waves appear at the margin, the most regular and largest 
one being in the middle, and from this point the margin becomes regularly arched with a semicircular profile, 
giving the adult shell a very gibbous, transversely fusiform figure, sometimes rendered slightly rhomboidal by 
the prominence of the middle, the gibbosity of the middle of the shell gradually passing into the conoidal ears ; 
cardinal area of both valves rhomboidal if taken together, ten times wider than high, that of the receiving valve 
nearly twice as wide as that of the entering valve, and its edge set with about nine or ten small, short, triangular 
spines, directed strongly outwards and backwards on each side of the beak. Entering valve nearly as concave 
as the receiving one is convex. Surface of both valves marked with fine, close, flexuous, rounded strize, crossed by 
microscopic lines of growth, separated by very narrow, strongly punctured, impressed lines, almost uniform in 
size on all parts of the shell (fourteen in two lines at ten lines from the beak, the same number in the same 
space at four inches from the beak); substance of the shell thick. Internal casts of receiving valve in old 
specimens marked with coarse pits, and small elongate lacunz, forming a very coarse, interrupted, irregular 
suleation near the margin; adductor impressions large, ovate, but not very deeply defined. Proportions of 
6 
small specimens two and half inches wide, proportional length %, depth of both areas ,°,, depth of receiving 
valve greatest at one-third from the beak, varying from 35 to 4; adult specimens seven inches wide, proportional 
length =, depth *, thickness of the shell at this latter size two lines. 
This beautiful species seems extremely different in its young and old stages, the young being semicircular 
and flattened or only moderately gibbous in the middle, and very regular; while the adult has some of the irre- 
gular, unsymmetrical, rounded, longitudinal folds, as well as the size and general form of Producta gigantea. 
Even in the young state, however, as I have mentioned, there is great variation in the depth of the receiving 
valve, no two specimens being exactly alike. To the flattened ones M. de Verneuil and M.de Koninck retained 
Mr Phillips’ specific name of Papilionacca, and to the more gibbous forms they apply Sowerby’s name, comoides. 
This latter species of Sowerby I think to be an entirely different shell of great rarity{(of which a specimen exists 
in the Bristol Museum), having coarser strise, broad, nearly parallel-sided, cardinal area, &c. In all its 
varieties the very fine, uniform, close, flexuous strize distinguish this species from any others of similar size. 
Even the limits in the dimensions of the striee given by M. de Koninck in his Monograph of Chonetes for 
papilionacea, shew that there is no difference in this respect between that and the shell he gives as C. comoides, 
although he seems to consider this supposed difference a distinguishing character for the two species; the other 
distinction, viz. the young being wider than the old, is commonly seen in the allied species. 
[easc. 111.] 3N 
